Japanese Laid-open Patent Publication No. 2009-144914 discloses a fastener that joins a plurality of base materials together by pressure fitting cylindrical sleeves each of which has a flange into through holes that are formed on the base materials and then inserting and attaching rivets into the sleeves. This sleeve is used for purposes such as protecting the through hole, maintaining an electrical connection and the like. Incidentally, when a sleeve having a wrong length is pressure fitted into the through hole, it becomes necessary to remove the sleeve from the base material. However, there is a problem in that because the sleeve is extremely thin, the sleeve cannot be grasped using a tool, and so removal is difficult. Therefore, there is a feasible method of removing the sleeve from the base material in which by screwing a tap into the sleeve and cutting a screw into the inner surface of the sleeve, the sleeve and tap become engaged and the tap is pulled out from the base materials.
With this kind of method, the tap remains screwed into the sleeve, so the sleeve must be removed from the tap. However, for example, in the case of grasping the sleeve with a tool such as a pair of pliers and removing the sleeve from the tap by turning the tap, there is a problem in that because the sleeve is extremely thin, there is a possibility that the sleeve may be damaged.